Semirigid airfoil for airborne vehicles

ABSTRACT

The present invention relates to a semirigid airfoil for use with airborne vehicles and capable of being folded and/or warped. The airfoil includes a rigid spar defining a leading edge and a cable defining the trailing edge with the root end thereof secured to the fuselage of the vehicle and the other end to a tip truss structure, with a flexible material forming top and bottom airfoil surfaces. Means are also provided for twisting portions of the airfoil about an axis extending through the root end, and means for pivoting the spar to fold against the fuselage.

FIPB301 XR United States Patent 54 SEMI-RIGID 'AIRFOIL' ron AIRBORNEvEme s 15 Claims, 1 1 Drawing Figs.

[52] U.S. Cl 244/38, 244/1 SS, 244/46, 244/48, 244/49, 244/6 [51] Int.Cl 1364c 1/26, B64c 3/52, B640 3/56 [50] Field of Search 244/44, 43, 46,48; 49, 6, 38

[56] References Cited UNITED STATES PATENTS 7 2,288,829 2 1942 New rnanv 244 3s x 1,856,578 5/1932 Migueletal; 244 44 1,875,891 9/1932SalisburyetaL. 244/6 291 .788 4/1937 Adams.... 244/44x 2,961,196 11/1960Athinson.. 244/46 3,135,482 6/1964 Girard 244 43 3,330,501 7/1967Barber... 244 43x 3,446,458 5/1969 R0gallo.... 244/43 3,463,420 8/1969Butleretal. 244 43x Primary Examiner-Milton Buchler AssistantExaminer-Jeffrey L. Forman Attorney-Darby and Darby ABSTRACT: Thepresent invention relates to a semirigid airfoil for use with airbornevehicles and capable of being folded and/or warped. The airfoil includesa rigid spar defining a leading edge and a cable defining the trailingedge with the root end thereof secured to the fuselage of the vehicleand the other end to a tip truss structure, with a flexible materialforming top and bottom airfoil surfaces. Means are also provided fortwisting portions of the airfoil about an axis extending through theroot end, and means for pivoting the spar to fold against the fuselage.

PATENTEU mm 1 I97! 3599,5304

sum 1 or 4 INVENTORS THOMAS E. SWEENEY PHILIP M. CONDIT ROBERT A.ORMISTON WALTER BARRY NIXON W 7&0? ATTOR EYS PATENTEI] nus! 7l 97| I 3'599- sum 3 0F 4 INVENTORS THOMAS E. SWEENEY PHILIP M.

ROBERT A.O STON WALTER BARRY NIXON Y ATTORN Y5 PATENTEU AUG 1 7 |97|SHEET 0F 4 FIG. ll

THOMAS E. SWEENEY PHILIP M. CONDIT ROBERT A. ORMISTON WALTER BARRY NIXONf ATTORNEY SEMEB QED 52 3.501! O QRNEYEHK ES This invention relates tosemirigid airfoils, or sailwings, and more particularly to apparatus forwarping and/or folding semirigid airfoils.

The use of airfoils of semirigid construction in which a rigid sparsupports a flexible wing from dates back to the earliest successesenjoyed by the pioneers of flight. The predominant use of rigid wingedaircraft in present commercial flights is well known. Ailerons presentlyperform functions, such as roll control, which were accomplished bywarping or twisting of the former flexible wings in order to createunequal or opposing lifting forces on opposite sides of the aircraft.

Rigid wings presently known to the art are considerably more expensiveto fabricate than semirigid or flexible winged aircraft. Costs ofmaterials are necessarily passed on to the purchaser of such craft,which in many cases may be one of the growing numbers of persons who owna smallplane for pleasure or business.

Known aircrafthaving a high aspect ratio,such as gliders, have rigidwings which must be disassembled such that the aircraft can betransported between the place of storage and the airport. Suchdisassembly includes detaching the wing from the fuselage, this in mostcases requiring the work of at least two persons. Considerable time isconsumed and often tools are required to perform the operation. 7 i

It is an object of the present invention to provide a semirigid airfoilof the sailwing type which is foldable and capable of being warped atwill in predetermined magnitudes.

Another object of the present invention is to provide a warpingapparatus for a semirigid airfoil of the sailwing type.

A further object of the present invention is to provide a semirigidairfoil of the sailwing type for use with and as anextension of a fixedand rigid airfoil, the semirigid airfoil being foldable suchthat theleading edge thereof forms the wingtip fairing of the fixed rigid wingwhen in a folded position.

A yet further object of this invention is ;to provide a semirigidairfoil of the sailwing type for use with fixed wings as above,including apparatus for warping the form of the semirigid airfoil.

Another object of this invention is to provide a folding" semirigidairfoil of the sailwing type for use with a helicopter wherein thesemirigid airfoil provides means for increasing high-speed performanceof the helicopter by substantially un-' loading the rotor of thehelicopter during forward motionof the craft. g

A yet further object of the present invention is to provide a semirigidairfoil of the sailwing type for use with ahelicopter or other verticaltakeoff and landing aircraft wherein such airfoil includes means forwarping or twisting the form thereof.

Another object of the present invention is to provide a foldingsemirigid airfoil of the sailwing type in combination with a liftingbody or a spent rocket booster or missile, the folding airfoil providingmeans for maintaining arelatively shallow glide angle of the liftingbody.

The present invention fulfills the aforementioned objects and overcomeslimitations and disadvantages of prior art-solutions to existingproblems by providing a flexible semirigid airfoil of the sailwing typewhich may be folded and/or warped, and further providing specificapplications or uses of the sailwresponsive to movement of the controlstick. Thus movement of the control stick causes the truss to pivotabout the hinge axis, thereby changing the lifting forces on theairfoil. The pivoting of the truss according to the present invention isaccomplished with substantially no change in the trailing edge cabletension throughout the angular range of the warp, this resulting inminimal control forces being required to produce the warp. I

In embodiments of the present invention wherein the semirigid airfoil isstructurally combined with fixed rigid wings of an aircraft, the aspectratio of the wing is considerably increased with a relatively smalladdition of weight. A retractable wing tip comprising an airfoil of thesailwing type is hin-v gedly mounted to a conventional hard wing. Thespar of the sailwing forms a wing tip fairing when retracted.

In embodiments of thepresent invention wherein a folding semirigidairfoil of the sailwing type is structurally combined with a helicopteror other vertical takeoff and landing vehicles, high forward speedperformance of the craft is substaning. These applications include theuseof thefoldable and warpable sailwing structurally combined with rigidwings of a fixed-wing aircraft; a helicopter; a lifting body or amissile or rocket booster; or other aerodynamic structures.

The airfoil, in a preferredembodiment, includes a hinged rigid spardefining the leading edge of the sailwing. A cable extending between aroot point and the extremity ofthe airfoil defines the trailing edge ofthe sailwing. Warping means for twisting portions of the airfoil aboutanaxis extending through the root point includes a truss hingedlysecured to the spar for pivotal movement about the hinge axis extendingthrough the root point. A control stick for use by the pilot of thecraft is interconnected with the truss by a plurality of cables andpulleys tially increased by the unfolding or deployment of a foldablesailwing once the craft is lifted to the desired altitude and forwardspeed is experienced.1The sailwing is maintained in the folded orretracted position during liftoff in order to eliminate high downloadswhich would be produced if the airfoil were in the rotor downwash.Similarly, the semirigid airfoil can be retracted in order to avoidaerodynamic blockage to the rotor system in autorotational descent.

The embodiments of the present invention employing a foldable andwarpable sailwing in structural combination with a lifting body or amissile or rocket booster, include means for enabling a shallow glideand lower speed landing of such lifting bodies after reentry fromextraplanetary spatial vacuum into the atmosphere. The sailwing isfolded ina stowed condition within the lifting body until reentry of thelifting body into the atmosphere, whereupon the sailwings are deployed.Deployment is accomplished, in one embodiment of the present invention,by means of solid propellant rockets disposed at the tips of thesemirigid airfoils which, in a preferred embodiment of the invention,will be interconnected to prevent the deployment of one airfoil withoutthe other, and to further cause both airfoils of an aircraft to bedeployed simultaneously. The thrust of the rockets carry each airfoilfrom a stowed position to an unfolded or fully operable position. It iswithin the scope of the present invention to include means forcontrolling the descent of the lifting body through-the atmosphere suchthat a precise descent pattern or flight path may be predetermined.

The invention will be more clearly understood from the followingdescription of specific embodiments of the invention together with theaccompanying drawings, .wherein similar reference characters denotesimilar elements throughout the several views, and in which:

FIG. 1 is a fragmentary schematic plan view of wing warping apparatusaccording to the present invention;

FIG. 2'is an enlarged fragmentary sectional plan view of a tip portionof the wing of FIG. 1;

FIG. 3 is a schematic end view of the wing tip shown in FIG. 2, lookingalong lines3-3 of FIG. 2;

FIG. 4 is a fragmentary schematic perspective view of a warping controlsystem according to the present invention;

FIG. 5 is a top plan view of an aircraft employing sailwingtype tipsaccording to the present invention with the tips shown ina retractedposition;

FIG. 6 is atop plan view of the aircraft shown in FIG. 5 wherein thesailwing tips are in a deployed position;

- FIG. 7 is ,a' top plan view of a helicopter. equipped with foldableand warpable sailwings according to the present invention;

FIG. 8 is an elevational view of the helicopter shown in FIG. 7 in whichthe sailwings are deployed;

FIG: 9 is an elevational view of a rocket equipped with foldingsailwings according to the present invention;

. FIG.' 10 is a perspective view of the rocket shown in FIG. 9 in whichthe sailwings are deployed; and

FIG. 11 is a perspective view of a lifting body in the form of anextraplanetary vehicle equipped with folding sailwings according to thepresent invention.

FIGS. 1 and 2 show a semirigid flexible airfoil of the sailwing type.For purposes of illustration, the preferred embodiment of the sailwingairfoil shown in FIG. 1 is described as a wing for an airborne body suchas an aircraft.

The wing assembly 10 shown in FIG. 1 includes a rigid spar 13 which ishinged at point 11 to fuselage 12 of the vehicle with which wing 10 isto be used. Rigid spar l3 defines the leading edge of the airfoil 10 andis hollow in the preferred embodiment shown in FIG. 1. The material ofspar 13 may be wood, metal or other suitable material. Atriangular-shaped truss assembly 14 is secured on its base leg 20 forpivotal movement about a hinge axis 15 near the end of spar 13 by a pairof support struts l6 and 17. Support struts l6 and 17 are formed withbearing portions 18 and 19 respectively, at one end of each. Theopposite ends of these struts are secured, such as by welding, to sparl3.

.Truss assembly 14 is formed in a triangular shape, although anysuitable polygonal configuration is within the scope of the presentinvention. The base, or first, leg 20 of the truss as sembly is disposedcoaxially with respect to hinge axis 15 and is journaled within bearingportions 18 and 19 of support struts 16 and 17, respectively. The secondand third legs 21 and 22 of the truss 14 extend from opposite ends offirst leg 20 and terminate in a tip portion 23. A wing tip 54 is securedalong one of its edges to the leg 22 of the truss and therefore moveswith the truss as it pivots within the bearings 18 and 19.

A cable 24 has one end secured to the tip 23 of the truss 14 and itsother end to a root point 25 on the fuselage 12. Cable 24 defines thetrailing edge of airfoil 10. Alpiece of flexible material 26 extendsfrom a first edge forwardly around the spar 14 without attachmentthereto so as to allow wing warping and thence back to its first edgewhere it is seamed. The seam constitutes the trailing edge of theflexible material and is formed in the shape of a catenary are forproviding chordwise tension in a direction parallel to the centrallongitudinal axis of the aircraft supporting the airfoil. The seam issecured to cable 24, such as by providing eyelets or lacing secured tothe seamthrough which cable 24 is passed. Material 26 is preferably madeof dacron sailcloth impregnated with silicon, but may also be canvas,plastic or other suitable flexible material and it defines the shape ofthe airfoil. The tension in wing material 26 is controlled by varyingthe tension in cable 24.

As shown in FIG. 1, the hinge axis 15 for the truss 14 extends coaxiallywith respect to the base leg 20 and thereafter through the fuselage rootpoint 25. A catenary defined by cable 24 extends from trusstip portion23 tangentially with respect to and terminating a toot point 25. Thus,pivoting or rotation of truss assembly 14 about its hinge axis 15results in constant tension in cable 24 since the distance between thetip.

23 and root point 25 remains constant during all angles of warp. It isthe maintenance of constant tensile stresses in cable 24 which minimizescontrol forces. This is described below.

As seen best in FIGS. 2 and 4, horn member 27, having an upper end 28and a lower end 29 is rigidly secured, such as by welding, to anextension of the truss base leg 20. The portion of the horn between thebase leg 20 and each of its ends 28 and 29 defines a lever arm whichgives rise to a mechanical advantage when forces are exerted on eitherof these ends to effect pivoting of truss assembly 14 about hinge axis15. Of course the length of this lever arm may be of different lengths.

FIG. 4 shows a preferred mechanism for controlling the magnitude ofpivotal movement of truss assembly 14, and thus A pair of arms 35 and 53are fixed to hub 33 and extend radially from the hub and coaxially withrespect to each other. Control cables 36 and 37 are secured to arms 35and 53 respectively, and extend around pulleys 38 and 39. The cable 36passes around pulleys 38 and 40 to an arm 42 which is fastened to a hub44. Similarly, cable 37 passes around pulleys 39 and 41'to an arm 43 onthe hub 44. Arms 42 and 43 are secured to and extend radially from hub44 which, in turn, is fixedly secured to a support rod 45 which ismounted on the vehicle body.

A second pair of arms 46 and 47 are also secured to hub 44 and extendradially therefrom and coaxially with respect to each other. The axes ofarms 42, 43 and 46, 47 are preferably perpendicular with respect to eachother.

A second pair of control cables 48 and 49 are secured to arms 46 and 47,respectively. This pair of cables extends through spar 13, aroundpulleys 50 and 51, respectively, which are also located within the spar.The ends of the cables 48 and 49 are secured to the upper and lower endsof 28 and 29 of the horn member 27. Pulleys 50 and 51 are mounted forrotation to a support bar 52, which is secured to spar l3 and located inthe spar interior.

FIG. 4 is a fragmentary view of the control system and shows only onecable arrangement for controlling one wing airfoil. Extensions 48A and49A of cables 48 and 49, respectively, are also shown broken off ordiscontinued. It should be understood that a symmetrical or mirror imageof the abovedescribed pulley and horn member arrangement exists for anairfoil (not shown) on the opposite side of the aircraft. Cable 48 andextension 48A, while shown coaxially with respect to each other, areeach secured to arm 46. Similarly, cable 49 and extension 49A are eachsecured to arm 47. Thus, pivoting of hub 44 by manipulation of controlstick 31 will cause opposite movement of the horn members on oppositesides of the vehicle. This necessarily results with the structure ofFIG. 4 because increases in tension in either of cables 48 and 49results in decreases in tension or slackening in their counterparts 48Aand 49A.

In operation of the bridle control system of FIG. 4, the pilot movescontrol stick 31 either to the right or left (R or L in FIG. 4) toeffect warping. As an example, movement of control stick 31 to the rightlifts arm 35 of hub 33 which results in increasing tension in controlcable 36. This causes a downward pivotal movement of arm 42 on hub 44about the axis of support rod 45. The resulting pivoting of hub 44causes an increase in tension in control cable 48, thereby moving upperend 28 of horn member 27 toward pulley 50. Movement of horn member 27 inthis direction results in pivoting of truss assembly 14 upward with anassociated warping of the form of wing assembly 10. In a like manner,movement of the control stick 31 to the left produces tension in cable37 which acts tt move arm 43 of hub 44 down, thereby applying tension tocable 49. and moving the truss l4 downward.

FIG. 3 shows several airfoil configurations which can be achieved bymovement of the control system and subsequent operation of the warpingcontrol. Reference numeral 23a represents the location of truss tip 23of the truss when in an unwarped, or neutral, position. Upon movement ofcontrol stick 31 to the right as described above, truss tip 23 ispivoted upward, for example to the position designated 23b in FIG. 3.Movement of control stick 31 to the left moves truss tip 23 down, forexample to the position shown in 236. For the case where truss tipportion 23 is moved to the position designated 230 from position 23a, anincrease in the angle of attack is achieved, resulting in a tendency ofthe airfoil to lift. For the case where truss tip portion 23 is moved tothe position designated 23b from position 23a, there is a tendency ofthe airfoil to sink. BY upward warping of wing 10 and downward warpingof the wing opposite wing 10, not shown, the unequal lifting forces onthe respective wings result in rotation of the aircraft about itscentral longitudinal axis. Of course it is within the scope of thepresent invention to include warping in selected amounts within theextreme most positions 23b and 230 schematically shown in FIG. 3, and tofurther provide a locking of the airfoil at preselected magnitudes ofwarp. It is also obvious from FIG. 3 that the distance between any ofpoints 23a or 23b or 23c and root point 25 remains substantiallyconstant throughout the warping operation, since the locus of pointsdefined by tip 23 during its movement is a curve of substantiallyconstant radius.

In the preferred embodiment of the control structure shown in FIG. 4,upward movement of tip portion 23 is one wing will necessarily result indownward movement of the tip portion of the aircrafts opposite wing,since increases in tension in control cable 48, for example, will beaccompanied by decreases in tension in its counterpart. It is alsopossible to include individual controlling of warping for each airfoil(wing) or sailwing when two or more are used.

Deployment of wing assembly from a folded to an unfolded position, thelatter position illustrated in FIG. 1, is accomplished by a hydrauliccylinder assembly 5 which includes a cylinder 6 and a push rod 7. Thecylinder is secured to the fuselage 12 and the rod is secured to spar 13at point 8 such that its reciprocating movement moves the wing assembly10. Thus, on rod 7 retracting into cylinder 6, wing assembly 10 isfolded in a pivoting motion about hinge point 11 in toward the fuselage.In the deployed position shown in FIG. 1, hydraulic pressure maintainsrod 7 in an unyielding and rigid manner against loads upon wing assembly10 tending to cause pivotal movement of the assembly about point 11. Thecontrol circuit for the cylinder assembly 5 is not shown, but it can beof any suitable conventional construction. It is within the scope of thepresent invention to include other means for deploying folding wingassemblies, such as overcenter-lock linkage.

FIGS. 5 and 6 show retractable sailwing airfoil tips used in combinationwith conventional hard wings of an aircraft. This arrangement permitsthe wing area and aspect ratio to be altered in flight by an amountcorresponding to the area occupied by the sailwing tips. It is intendedthat the airfoil and control means described above for FIGS. 14 becharacteristic of thesailwing tip described in FIGS. 5 and 6, and theother applications described below in FIGS. 71l.

In FIGS. 5 and'6 an aircraft 60 includes a conventional fuselage portion61, tail portion 62 and two hard wings 63 with ailerons 63a.Sailwing-type tip assemblies 64 and 65 are hingedly secured to each ofthe wings 63 at points 66 and 67.

Sailtip assemblies 64 and 65 are similarlyin structure to the wingassembly l0of FIGS. 1-4 already described. Only tip 64 is describedsincethe other tip 65 is similar. A rigid spar 68 (FIG. 6) defines theleading edge of either of the tips 65 or 64, and a trailing edge cable69 defines the trailing edge. In the retracted position shown in FIG. 5,spar 68 becomes the wing tip fairing of wing 63. By deploying thesailwing tip assemblies 64 and 65, the aspect ratio and wing area areincreased, providing both a lower wing loading and increased induceddrag efficiencies. The term aspect ratio, as used herein, is the ratioof wing span to the mean chord dimension of the Wing.

The sailtip assemblies 64 and 65 can be deployed by the hydraulic andcylinder arrangement disclosed for wing assembly 10. During flight atrelatively high speeds, the pilot of the aircraft 60 will maintain thesailtip assemblies 64 and 65 in a retracted position, as shown in FIG.5. With the trips retracted, the requirements of low aspect ratio atsuch high speeds is met. At lower flight speeds, the sailtip assemblies64 and 65 are deployed thereby increasing the aspect ratio and wing area(See FIG. 6). Using the present invention, induced drag reductions of upto 40 percent are possible for landings with low aspect ratios sinceflight with the sailtip assemblies extended will result in an increasedaspect ratio with a resulting decrease in airflow downwash angle. Thusthe drag caused by lift and induced by the downwash resulting from thislift will also decrease. The increased wing area provides lower stallspeeds for landing of the aircraft.

The semirigid airfoil, or sailwing, according to this invention can alsobe used as an auxiliary wing for a helicopter. It is known that thecruise and high-speed performance of a helicopter can be substantiallyincreased by the addition of a relatively small wing to the craft. Thefunction of the semirigid wing in this case is to substantially unloadthe rotor, thereby permitting more efficient use of availablehorsepower, and to provide an airfoil capable of being folded out of thedownwash of the rotor.

FIGS. 7 and 8 show a helicopter 70 with the conventional fuselage 71 androtor 72. Helicopter 70 is equipped with two semirigid airfoil orsailwing assemblies 73 and 74, each assembly capable of folding back outof the downwash of the rotor. The folded position is illustrated forsailwing assembly 74, while a fully deployed or unfolded position isillustrated for assembly 73 in FIG. 7. The deployed position of assembly74 is shown by the dotted lines of FIG. 7. Sailwing assemblies 73 and 74each pivot about hinge point 75. Each=of sailwingassemblies 73 and 74 isstructurally similar to wing assembly 10 described for FIG. 1 above. Arigid forward spar 76 defines leading edge 77. Trailing edge cable 78defines the trailing edge of assembly 73. Flexible material 79 coversspar 76 and is secured to cable 78 to form the airfoil surface. A trussassembly 80 functions in much the same manner astruiss'assembly 14described for FIG. 1 where warping of sailwing assembly 73 is desired. 7

Folding and unfolding of the auxiliary wing assemblies 73 and 74 areaccomplished by a hydraulic cylinder assembly (not shown) or othersuitable means. The relative easy foldability of assemblies 73 and 74facilitates storage in a relatively small space in the fuselage, theflexible material 79 folding in an accordianlike fashion.

In operation, sailwing assemblies 73 and 74 are retracted for low speedand hovering flight regime and also for autorotational descent. Forcruising and high-speed flight, the sailwing assemblies are deployedfrom their folded position. In a preferred form of the invention thesailwing assemblies are preferably made capable of being folded flushwith the sides of the fuselage by providing receptacle wells in thesides of the fuselage. Flg. 8 also illustrates the appearance ofhelicopter 70 with sailwing assemblies 73 and 74 fully deployed.

The semirigid airfoil or sailwing of the present invention also can beused to allow recover of and controlling the postreentry characteristicsof spent rocket booster payloads, such as the type used in known defenseor aerospace missions. FIG. 9 shows a booster 82 equipped with sailwings83 and 84 folded along and into the sides of the booster main structure,as would be the case prior to or during launch. The spars of thesailwings are shown in FIG. 9. I-Iinged tips 85 and 86 which form thewingtip fairing for sailwings 83 and 84, respectively, similarly foldalong sides of the booster. An inflatable nose fairing 87 permits matingof the nose of the booster with its payload without interference.

Solid propellent rockets 88 are secured to each tip of sailwings 83 and84 or other suitable linkage to provide the forces necessary to deploysailwings 83 and 84 from the folded position shown in FIG. 9 to thefully deployed position shown in FIG. 10, deployment including apivoting of the sailwing assemblies about hinge points 89. T.=e thrustinitiation of the rocket is either preprogrammed or controlled by ignalsfrom a remote location.

In operation, after burnout, the sailwing assemblies 83 and 84 aredeployed by the rockets 88 and the nose fairing 8 would be automaticallyinflated, thereby transforming the separated booster into a glider whoseflight path and landing area is capable of control by conventionalelectromechanical remote control devices operated from a groundinstallation, for example. The inflatable nose fairing 87 reducesfuselage drag of the craft. The relatively expensive booster can berecovered without damage, facilitating its possible re-use.

FIG. 11 shows an extraplanetary reentry vehicle or lifting body 90having a shape determined by thermodynamic, hypersonic, supersonic andsubsonic aerodynamic parameters. Lifting body 90 provides an astronautwith a vehicle capable of making controlled glide-type landings on terrafirma rather than paraehuting into the sea. A transparent bubble 91provides means through which the astronaut may see to determine whetherchanges in flight path are necessary. Fins 92 aid in stabilizing thecraft 90 during its descent.

Folding sailwing assemblies 93 and 94 of the type previously describedfor FIG. 1 are hinged about hinge points 95 such that each sailwing willretractably fit into a slot in the sides of the lifting body. A majoradvantage of the use of such semirigid airfoils or sailwings is the factthat the shape of lifting body 90, as determined by the aboveparameters, may be retained for all'flight regimes other than merely thesubsonic glide phase. In this latter regime the sailwings are deployedin flight. thereby permitting flight characteristics approaching thoseof a conventional airplane, .with associated favorable handlingqualities.

The embodiments of the invention particularly disclosed are presentedmerely as examples of the invention. Other embodiments, forms onmodifications of the invention coming within the proper scope of theappended claims will of course readily suggest themselves to thoseskilled in the art.

We claim:

1. A control system for a vehicle comprising a semirigid airfoilattached to the vehicle, said airfoil including a cable which definesthe trailing edge thereof, means forming a rigid leading edge, andflexible material interconnecting the leading and trailing edges, saidcable being secured at one end thereof to the vehicle at a predeterminedpoint; and means independent of the aerodynamic forces acting on theleading edge for controllably twisting a portion of said airfoil remotefrom the end of the cable secured to the vehicle about an axis extendingthrough said point to change the warp of the airfoil, said twistingmeans being connected to said cable at a point to maintain constanttension therein through various angles of warp.

2. A control system as in claim 1 wherein said twisting means isconnected to the end of the cable.

3. A control system as in claim 1 wherein said twisting means includes aportion fixedly connected to said means forming said rigid leading edge.

4. Control apparatus for warping the form of a semirigid airfoil,comprising an airfoil supported from a vehicle and having a rigid spardefining a leading edge and a cable defining the trailing edge, saidcable being secured at a root end thereof to thevehicle at apredetermined point, a truss assembly, means for hingedly securing saidtruss assembly to the rigid leading edge for pivotal movement about ahinge axis extending through said point, and control means for movingthe truss assembly about its hinge axis.

5. Control apparatus according to claim 4, wherein said control meansincludes portions remote from said truss assembly.

6. Control apparatus according to claim 4, wherein said truss assemblyincludes a closed polygonal shaped truss member having a first armdisposed coaxially with respect to said hinge axis, and a horn memberintegral with said first arm and disposed at one extremity thereof, saidhorn member including first and second leg portions each extending fromsaid extremity, said truss member being integral with a tip end of saidtrailing edge cable opposite the root end, the distance between saidroot and tip ends remaining substantially constant during movement ofthe truss assembly.

7. Apparatus according to claim 6, further comprising bearing meanscarried by the spar, said first arm of said truss being journaled insaid bearing means.

8. Apparatus according to claim 6, wherein said control means includes afirst support rod, a tee-shaped control stick mounted for pivotalmovement about the axis of the first support rod and including a handleportion forming the base leg of the tee, and control arms forming therespective coaxial legs of the tee, a second support rod disposed alongan axis parallel to the axis of the first support rod and mounted forrotation about its axis, a cross-shaped element integral with the secondsupport rod having first and second pairs of diametrically opposed legsextending radially with respect to the second support rod, a pluralityof pulleys carried by the vehicle, a first pair of cables each securedat one end thereof to a control arm and at its opposite end to one ofsaid first pair of legs, each of said first pair of cables engaging andbeing guided by at least one of said vehicle-mounted pulleys, aplurality of pulleys supported by the spar, and a second pair of cableseach secured at one end thereof to one of said second pair of legs andat its opposite end to one of said first and second leg portions, eachof said second pair of cables engaging and being guided by at least oneof said spar-mounted pulleys.

9. Aerodynamic apparatus, comprising a body, an airfoil supported by aportion of the body including a rigid leading edge, a cable defining atrailing edge, and flexible material engaging said leading edge andextending for the entire distance between said leading edge and thecable for defining portions of the form of the airfoil; said cable beingsecured at an end thereof to the body at a predetermined point, meansincluding said cable for varying the warp of the airfoil, and means formoving said airfoil from a first inoperative position to a secondposition wherein said airfoil is deployed.

' 10. Aircraft apparatus according to claim 9 for use with a vehiclehaving a rigid fuselage wherein said airfoil includes a spar definingsaid leading edge, said moving means including means for pivoting thespar.

11. Apparatus for augmenting the aerodynamic properties of a rigid wingaircraft which comprises a fuselage, a rigid wing having a leading edgeand a trailing edge and being supported by the fuselage, an auxiliaryairfoil including a spar defining a rigid leading edge, a cable defininga trailing edge, and flexible material engaging said leading edge andthe cable for defining portions of the form of the airfoil, means forhingedly connecting the spar of said auxiliary airfoil to said fixedwing, means for moving said auxiliary airfoil from a folded to anunfolded position, said spar defining an extension of a portion of saidrigid wing when said airfoil is in an unfolded position and said cabledefining an extension of the trailing edge of said rigid wing when saidairfoil is in said unfolded position, said leading edge of the auxiliaryairfoil forming a wingtip fairing of said rigid wing when said airfoilis in said folded position.

12. Aircraft apparatus according to claim 11 further comprising a rigidmember integral with the spar of the auxiliary airfoil and forming apart of the outermost portions of the trailing edge of the rigid wingwhen said auxiliary airfoil is in the folded position, said rigid memberforming the outermost extremity of the auxiliary airfoil when unfolded.

13. Aircraft apparatus according to claim 12, further comprising meansfor warping the form of said auxiliary airfoil.

14. An aircraft, comprising a fuselage, an airfoil supported by thefuselage having a rigid leading edge and a cable which defines thetrailing edge thereof with the rigid leading edge and the cable beingsecured by flexible material, said cable being secured at one endthereof to the fuselage at a predetermined point, and means actingindependenlly of the aerodynamic forces on the leading edge forcontrollably twisting portions of the airfoil about an axis extendingthrough said point while maintaining constant tension in the cable atvarious angles of airfoil warp produced by said twisting.

15. An aircraft according to claim 14, further comprising means forfolding the airfoil with respect to the fuselage.

1. A control system for a vehicle comprising a semirigid airfoilattached to the vehicle, said airfoil including a cable which definesthe trailing edge thereof, means forming a rigid leading edge, andflexible material interconnecting the leading and trailing edges, saidcable being secured at one end thereof to the vehicle at a predeterminedpoint; and means independent of the aerodynamic forces acting on theleading edge for controllably twisting a portion of said airfoil remotefrom the end of the cable secured to the vehicle about an axis extendingthrough said point to change the warp of the airfoil, said twistingmeans being connected to said cable at a point to maintain constanttension therein through various angles of warp.
 2. A control system asin claim 1 wherein said twisting means is connected to the end of thecable.
 3. A control system as in claim 1 wherein said twisting meansincludes a portion fixedly connected to said means forming said rigidleading edge.
 4. Control apparatus for warping the form of a semirigidairfoil, comprising an airfoil supported from a vehicle and having arigid spar defining a leading edge and a cable defining the trailingedge, said cable being secured at a root end thereof to the vehicle at apredetermined point, a truss assembly, means for hingedly securing saidtruss assembly to the rigid leading edge for pivotal movement about ahinge axis extending through said point, and control means for movingthe truss assembly about its hinge axis.
 5. Control apparatus accordingto claim 4, wherein said control means includes portions remote fromsaid truss assembly.
 6. Control apparatus according to claim 4, whereinsaid truss assembly includes a closed polygonal shaped truss memberhaving a first arm disposed coaxially with respect to said hinge axis,and a horn member integral with said first arm and disposed at oneextremity thereof, said horn member including first and second legportions each extending from said extremity, said truss member beingintegral with a tip end of said trailing edge cable opposite the rootend, the distance between said root and tip ends remaining substantiallyconstant during movement of the truss assembly.
 7. Apparatus accordingto claim 6, further comprising bearing means carried by the spar, saidfirst arm of said truss being journaled in said bearing means. 8.Apparatus according to claim 6, wherein said control means includes afirst support rod, a tee-shaped control stick mounted for pivotalmovement about the axis of the first support rod and including a handleportion forming the base leg of the tee, and control arms forming therespective coaxial legs of the tee, a second support rod disposed alongan axis parallel to the axis of the first support rod and mounted forrotation about its axis, a cross-shaped element integral with the secondsupport rod having first and second pairs of diametrically opposed legsextending radially with respect to the second support rod, a pluralityof pulleys carried by the vehicle, a first pair of cables each securedat one end thereof to a control arm and at its opposite end to one ofsaid first pair of legs, each of said first pair of cables engaging andbeing guided by at least one of said vehicle-mounted pulleys, aplurality of pulleys supported by the spar, and a second pair of cableseach secured at one end thereof to one of said second pair of legs andat its opposite end to one of said first and second leg portions, eachof said second pair of cables engaging and being guided by at least oneof said spar-mounted pulleys.
 9. Aerodynamic apparatus, comprising abody, an airfoil supported by a portion of the body including a rigidleading edge, a cable defining a trailing edge, and flexible materialengaging said leading edge and extending for the entire distance betweensaid leading edge and the cable for defining portions of the form of theairfoil; said cable being secured at an end thereof to the body at apredetermined point, means including said cable for varying the warp ofthe airfoil, and means for moving said airfoil from a first inoperativeposition to a second position wherein said airfoil is deployed. 10.Aircraft apparatus according to claim 9 for use with a vehicle having arigid fuselage wherein said airfoil includes a spar defining saidleading edge, said moving means including means for pivoting the spar.11. Apparatus for augmenting the aerodynamic properties of a rigid wingaircraft which comprises a fuselage, a rigid wing having a leading edgeand a trailing edge and being supported by the fuselage, an auxiliaryairfoil including a spar defining a rigid leading edge, a cable defininga trailing edge, and flexible material engaging said leading edge andthe cable for defining portions of the form of the airfoil, means forhingedly connecting the spar of said auxiliary airfoil to said fixedwing, means for moving said auxiliary airfoil from a folded to anunfolded position, said spar defining an extension of a portion of saidrigid wing when said airfoil is in an unfolded position and said cabledefining an extension of the trailing edge of said rigid wing when saidairfoil is in said unfolded position, said leading edge of the auxiliaryairfoil forming a wingtip fairing of said rigid wing when said airfoilis in said folded position.
 12. Aircraft apparatus according to claim 11further comprising a rigid member integral with the spar of theauxiliary airfoil and forming a part of the outermost portions of thetrailing edge of the rigid wing when said auxiliary airfoil is in thefolded position, said rigid member forming the outermost extremity ofthe auxiliary airfoil when unfolded.
 13. Aircraft apparatus according toclaim 12, further comprising means for warping the form of saidauxiliary airfoil.
 14. An aircraft, comprising a fuselage, an airfoilsupported by the fuselage having a rigid leading edge and a cable whichdefines the trailing edge thereof with the rigid leading edge and thecable being secured by flexible material, said cable being secured atone end thereof to the fuselage at a predetermined point, and meansacting independently of the aerodynamic forces on the leading edge forcontrollably twisting portions of the airfoil about an axis extendingthrough said point while maintaining constant tension in the cable atvarious angles of airfoil warp produced by said twisting.
 15. Anaircraft according to claim 14, further comprising means for folding theairfoil with respect to the fuselage.